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Checking chassis twist


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Hi, I'm part way through dismantling a late MkIV Spitfire and have just taken the front suspension apart. The rhs looked perfectly normal with respect to the number of shims behind the wishbones, but the lhs had about 1/2" of shims on the rear arm and 1/4" on the front and they were quite a variety of shapes and thicknesses! I was wondering if this was down to the fact that someone had tried to align all 4 wheels with the currently fitted mixture of rear half shafts (short on the right and the correct longer one on the left). 

But, I think I'll check the chassis isn't twisted before I go much further. Looking at the diagram in the ROM and Haynes shows a plan view with diagonals which should intersect nicely on the centreline of the chassis. They give locations (A and E) for setting up the chassis to be horizontal with heights from the ground, but there is no side view to see where the heights are measured from. Is point A one of the front over rider mounts, is E the body mount or shock mounting hole?

Thanks, John.

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It could be down to a bent vertical link, damaged wishbone, in fact many things besides a dinged chassis.

Changing shims front to rear on a wishbone changes the castor angle. The distance the wishbone sits off the chassis affects the camber.

Plenty of guides on how to set a car up are out there on the web. I did mine with string, tape measure, and a home-made camber gauge (bit of wood, string and a small weight). Nothing complex required to do a good job, just a bit of reading and time. All done once the car is ready for the road, and again once the car is "shaken down" and settled.

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Just been thinking about the height of the chassis from the ground and realised that it doesn't really matter as long as it's level side to side. Having the front or rear higher should only  move the intersection points along the centre line if it's all straight.

John. 

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Most chassis seem to have a slight twist if you check them. I guess the best check is to strip the chassis and stand it upright. If I jack my car up and put it on 4 axle stands, there is always a small gap at one stand, but the chassis settles down if left for a few days. The cars are a bit flexible I am afraid, so don't get too hung up on it.

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and camber is always checked by the total angle of both sides and   halve it 

 . on the road the chassis has no idea of upright so any difference side to side is pretty undetermined  

youre not the first to have long and short shafts mixed up .  hope you didnt get over complicated before you got the trap ???

Pete

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